1. Field of the Invention
The present invention relates to a drive control method for a motor used in a CPU cooling device or the like, and to an apparatus therefor.
2. Description of the Relevant Art
A CPU cooling fan motor in which an oil bearing is used as a bearing for necessity of miniaturization is proposed. The service life of the oil bearing is shorter than that of a ball bearing; and such service life becomes short with an increase in load on the bearing. The service life of a motor depends on the service life of the bearing. Therefore, a load on the bearing is desirably avoided.
For this reason, m a conventional cooling fan, the temperature of a heat-generating member (such as, a CPU) is detected every predetermined period of time; and when the detection value becomes larger than a predetermined threshold value, the motor is driven to cool the heat-generating member. When the temperature detection value becomes smaller than the threshold value by cooling, rotation of the motor is stopped; thereby, interrupting the cooling operation. More specifically, a temperature range in which the heat-generating member must be cooled, and rotation/stop of the motor is controlled as needed; thereby, making a load on the bearing lower than that in a case wherein the motor is continuously rotated for a long period of time. With such structural arrangement, the service life of the motor is designed be prolonged.
In the above-described conventional motor drive control, only the rotation/stop of the motor is controlled by comparing a predetermined threshold value and a temperature detection value. For this reason, when the temperature of a CPU or the like to be cooled sharply changes, and the drive/stop of the motor is frequently repeated, an instantaneous impact generated when the motor is driven to start its rotation or when the motor in a rotating state is stopped increases a load acting on the bearing. Therefore, the load on the bearing in this case is similar to the bearing in a case whereby the motor is continuously rotated, and the conventional motor drive control has a problem in that the service life of the motor cannot be prolonged.